After two weeks of work writing scripts to automate the creation of
new production/test boxes for $WORK, and two days to get it into a
state where I could post the result on Github without spilling all our
internal secrets, I am pleased to announce
Goldleaf. From the README:

Goldleaf is a tool for creating consistent and repeatable KVM Debian system images in which the packages installed, the versions of each package, and the answers to “debconf” configuration questions are specified precisely.

The package manifest and configuration files are text-based and are intended to be kept under Git version control.

The name ‘goldleaf’ comes from the article Golden Image or Foil Ball by Luke Kanies. On which note: it is unclear to me whether he would see this script as a good thing or as a bad thing, but I would argue that even if you reduce the number of images under your control to a single “stem cell” image, being able to recreate (any current or previous version of) that image on-demand is just as valuable as being able to recreate (any current or previous version of) any other application.